The invention relates to a method of producing a vehicle interior lining, especially a dashboard having a carrier part and, attached to the carrier part, a gas bag module containing a gas bag carrier and a gas bag that has a folded package section. The invention also relates to a vehicle interior lining.
Vehicle interior linings are manufactured in the largest possible sections in order to save assembly costs. This also applies to the dashboard that has to contain a passenger-side gas bag in modern vehicles in order to protect the passenger against injury in case of an accident.
In order to make the interior of the vehicle more comfortable for an occupant, in some cases, parts of the vehicle interior lining, also including the dashboard, are covered with a soft, resilient foamed material. The foam layer alone is not dimensionally stable enough, as a result of which it is applied onto a carrier part that consists, for example, of a harder injection molded plastic or of pressed materials, and that defines the shape of the vehicle interior lining. Until now, a gas bag module, for example, for a passenger-side gas bag, has been mounted under the carrier part so that the outlet opening of the gas bag is covered by a section of the carrier part. This section of the carrier part, which can be configured, for instance, as a conventional flap, can be dispensed with if the carrier part is covered with a foam layer, since the dimensional stability of the foam layer that is applied onto the carrier part is sufficiently high to create an esthetically pleasing surface that protects the gas bag underneath from being damaged. This gives rise to the decisive advantage that it is possible to dispense with the otherwise necessary separate covering flap, which is made of a rigid plastic material and is attached to the carrier part either by means of complex hinge mechanisms or else which has to have predetermined breaking points that are complicated to create.
U.S. Pat. No. 5,711,545 describes such a vehicle interior lining. At the desired place, the carrier part forms a receptacle for the gas bag module in the form of an depression, the folded gas bag being placed in such a way that it fills the depression. A flexible protective layer, which can be, for example, a paper-based product and which does not contribute to the stability, is placed over the gas bag. A plastic layer, which forms the visible part of the lining and makes a one-piece transition to the cover of the gas bag module, is foamed over this flexible protective layer, which is supposed to prevent the foamed material from penetrating into the gas bag module. For this purpose, the gas bag module is premounted on the carrier part, covered with the flexible protective cover, inserted into a foaming mold and foamed. During the foaming process, it can happen that the folded gas bag package is compressed by the pressure that prevails in the foaming mold. When the pressure subsides, the gas bag package decompresses again, as a result of which the surface of the foam layer can be detrimentally affected.
Therefore, the object of the invention is to propose a method with which such a detrimental effect cannot occur. Moreover, a vehicle interior lining, especially a dashboard, is to be provided that allows an especially fast deployment of the gas bag, whilst nevertheless, only small forces are transmitted to the vehicle occupant by the unfolding gas bag.
The method according to the present invention of producing a vehicle interior lining, especially a dashboard, provides that the lining has a carrier part and, attached to the carrier part, a gas bag module containing a gas bag carrier and a gas bag that has a folded package section (package-like folded section of the gas bag). The method comprises the following steps:
the gas bag, together with its package section, is placed into a gas bag receptacle that is formed on the gas bag carrier and that has an outlet opening for the gas bag;
the outlet opening is at least partially closed in an area of the package section by a rigid means;
an outside surface of the carrier part is foam-encapsulated with a plastic layer in a state in which the gas bag module is connected to carrier part.
By means of the rigid means, a compression of the package section of the gas bag is avoided during the foaming process so that no impairment of the surface of the foam layer can occur.
The carrier part advantageously has an opening for the unfolding of the gas bag, and the gas bag as well as the gas bag carrier lie in the projected area of the opening, i.e. in the opening or below it. Therefore, the foam layer is foamed onto the gas bag module directly, that is to say, without a stable intermediate layer.
The means preferably has such a strength that it is not substantially deformed by the pressure that is generated during the foaming process, so as to avoid a compression of the package section. The pressure in the foaming mold used is preferably between 2 and 10 bar, and especially preferably between 3 and 5 bar. Conventional foaming machines can be employed in this pressure range.
The deformation of the means is advantageously less than 5 mm and especially preferably less than 3 mm. A compression by this amount can be compensated for in the foam layer itself.
In order to prevent foam from penetrating into the gas bag module and in order to protect the gas bag module from environmental effects, a plastic foil is preferably arranged directly over the means before the carrier part is foam-encapsulated.
The method is especially well-suited for use with a gas bag carrier in which the gas bag receptacle is formed continuously along the edge of a middle plate of the gas bag carrier. Such a gas bag carrier can be used for modules that are particularly flat in shape and that have a relatively large lateral expansion, which is desirable for passenger gas bags. The middle plate is preferably flush with the outer surface of the carrier part and offers the necessary support for the foam layer in this area of the opening.
In order for the means not to interfere with the deployment of the gas bag out of the outlet opening of the gas bag receptacle during the unfolding of the gas bag, the means preferably has such a low strength that it frees the outlet opening in response to a force that is being exerted on the means by the unfolding gas bag when the gas bag module is activated. This can be achieved in that predetermined breaking points are provided at a suitable place in the means. Since the means can have much smaller dimensions and a lower weight than a conventional covering flap, the risk of injury to a vehicle occupant is low.
In a preferred embodiment of the method according to the invention, after the gas bag has been placed into the receptacle, the outlet opening is constricted in that the receptacle is compressed. In this case, the means is formed by the edge sections of the gas bag receptacle, which cause a constriction. No additional parts have to be used, which reduces the costs. Since the gas bag expands to a certain degree into the sections of the receptacle when it unfolds, thus freeing the outlet opening again, no loose parts are created that could be hurled into the vehicle interior. It is also possible for the gas bag receptacle to be compressed all the way down to just a narrow gap through which the gas bag can be pulled out of the gas bag receptacle when the gas bag unfolds. Thus, no additional force has to be used to free the outlet opening.
The invention also relates to a vehicle interior lining that is preferably made by a method according to the invention. In a preferred embodiment of such a vehicle interior lining, the means is a frame with a U-shaped profile that surrounds the gas bag receptacle, the open side of the U-shaped profile facing the inside of the frame and one leg of the U-shaped profile at least partially closing the outlet opening. After the package section of the gas bag is placed into the gas bag receptacle, the frame, which preferably has a certain amount of flexibility, can be placed onto the surrounding gas bag receptacle. The clamping that can be achieved in this manner can be selected in such a way that no further attachment is necessary. The component is simple to mount since it simply has to be placed over the gas bag receptacle.
In another preferred embodiment of the vehicle interior lining, the means is constituted by a projection of the carrier part. In this manner, no additional component has to be provided. When the gas bag module is attached onto the carrier part, the gas bag receptacle is arranged below the projection so that the projection at least partially closes the outlet opening.
In yet another preferred embodiment of a vehicle interior lining, the means is constituted by a projection formed on the gas bag carrier. In this case as well, no additional component has to be provided.
The gas bag carrier can be made of plastic. This makes it possible to shape the projection as well as the gas bag receptacle onto the gas bag carrier in a single manufacturing step.
In the two latter embodiments, the gas bag receptacle can be laterally open along its outer circumferential edge. From the open side, the package section can be placed into the gas bag receptacle. In order to protect the gas bag against environmental influences, the open side can be covered by a flexible cover, e.g. a plastic foil. This flexible cover can also serve to keep the package section in its folded state.
The invention also relates to a vehicle interior lining preferably produced by means of the process according to the invention, comprising a carrier part made of a hard material and a foam layer made of a soft foamed material that covers an outer surface of the carrier part and that is at least partially connected to said carrier part, the carrier part having an opening and the foam layer covering and closing off the opening, and comprising a gas bag module that is integrated into the vehicle interior lining and that has a gas bag carrier having a middle plate that is at least partially surrounded by a gas bag receptacle to accommodate the gas bag, only one single gas bag layer extending over the middle plate, and the gas bag carrier being arranged in such a way that the middle plate lies in the projected area of the opening in the carrier part, i.e. preferably in or under the opening. Because of the middle plate and due to the fact that only one single layer of the gas bag lies over the middle plate, a flat unfolding of the gas bag can be achieved. This is especially advantageous for use for a passenger gas bag in a dashboard. The middle plate preferably assumes the support function of the carrier part for the foam layer in the area of the gas bag module. In this manner, the foam layer cannot be compressed from the outside, and the formation of a hollow space between the gas bag module and the foam layer is avoided. Since there is only one layer of the gas bag on the middle plate, the gas bag situated in the area of the middle plate cannot have a negative effect on the haptic characteristics of the vehicle interior lining. After all, numerous layers would lead to a greater yielding of the foam layer in the area of the opening.
Advantageously, a section of the gas bag folded into a package is arranged in the gas bag receptacle.
The dimensions of the opening in the carrier part are preferably equal to or larger than the dimensions of the middle plate, so that either only the middle plate or else the gas bag receptacle lies in the projected area of the opening.
The middle plate preferably has an extension in its main direction of extension that is at least twice as large as two times the extension of the gas bag receptacle in the main direction of extension of the middle plate. The extension is measured along the middle plate, and the main direction of extension is defined as the direction in which the middle plate has its largest extension. The large extension of the middle plate in conjunction with the fact that only one single gas bag layer lies over the middle plate promotes the flat, rapid unfolding of the gas bag. Further, the gas bag has a large initial outlet surface.
Preferably, the gas bag receptacle is configured continuously around the middle plate in order to allow a simple accommodation of the gas bag. Moreover, in this case, a simple folding procedure can be used for the gas bag.
It is favorable if the middle plate is essentially flush with the outer surface of the carrier part so that the foam layer in the area of the middle plate cannot be pushed in and the gas bag module under the foam layer is not outlined on the outside.
There can be a foil between the gas bag module and the foam layer. The foil can be provided with a coating in order to prevent the foam layer from becoming detached in the area of the gas bag module.
An outlet opening of the gas bag receptacle is preferably at least partially closed off by a rigid means. The means can extend in the area of the opening between the foam layer and the gas bag that is accommodated in the gas bag receptacle. This is especially favorable if the gas bag receptacle is also arranged underneath the opening since the rigid means prevents a compression of the foam layer over the section of the gas bag that is accommodated in the gas bag receptacle and that has several layers. The means can be formed by a constriction of the gas bag receptacle.
It is possible to configure the means in such a way that, as a result of a force that the unfolding gas bag exerts on the means when the gas bag module is activated, said means is moved in such a way that the outlet opening of the gas bag receptacle is freed. The gas bag can then unfold from the entire outlet opening.
As an alternative, it is possible to configure the means in such a way that it only partially closes the outlet opening of the gas bag and that it is so rigid that it keeps sections of the outlet opening closed, even while the gas bag is unfolding. The gas bag is then pulled out of the gas bag receptacle one piece at a time, so to speak.
The means can be configured as a cover placed on the gas bag receptacle, which allows simple assembly.
Preferably, the top of the means is essentially flush with the outer surface of the carrier part in order to prevent the gas bag module from being outlined under the foam layer.
In a possible embodiment, the gas bag carrier is attached to the bottom of the carrier part. A gas generator carrier can be formed in one piece with the gas bag carrier.
As an alternative, the gas bag carrier can be attached to the carrier part via a gas generator carrier that is configured as a separate part.
Preferably, the vehicle interior lining is a dashboard.